Hermetic seal

ABSTRACT

An insulator to metal hermetic seal for electronic components and methods of making the hermetic seal. The hermetic seal may be a glass to metal or a ceramic to metal seal. The terminal member of the seal, whether glass to metal or ceramic to metal, may include a metal selected from the low-carbon steels, the Group I metals (copper, silver and gold, or alloys thereof or clad materials thereof), the Group VIII metals (nickel, palladium and platinum or alloys thereof or clad materials thereof), ironnickel-cobalt alloys or clad materials thereof, nickel-iron alloys or clad materials thereof, chromium-iron alloys or clad materials thereof or a metal from any one of the film-forming metals which can form an electrolytic oxide film such as tantalum, aluminum, niobium, titanium, zirconium alloys thereof or clad materials thereof. The glass member may include any one of the borosilicate, potash-soda-barium, potash-soda-lead, sodalime or aluminia-silicate glasses. The ceramic member may include any one of alumina, steatite, fosterite, or beryllia.

United States Patent Wallis et al.

3,646,405 [451 Feb. 29', 1972 [54] HERMETIC SEAL 3,305,624 2/1967 Wagner174/525 [72] Inventors: George Wallis Lexington; John J. Dorsey3,398,340 8/1968 Geoghegan ..3l7/260 m g g zg mumps Norwood PrimaryExaminer-James D. Kallam Attorney-Richard H. Childress, Charles W.Hoffman, Robert [73] Assignee: P. R. Mallory & Co. Inc., Indianpolis,lnd. E. Meyer and Henry W. Cummings [22] Filed: Jan. 8, 1969 [57]ABSTRACT [21] Appl An insulator to metal hermetic seal for electroniccomponents and methods of making the hermetic seal. The hermetic seal[52] US. Cl ..3l7/230, 317/242, l74/50.61 may be a glass to metal or aceramic to metal'seaL Th re [51} Int. Cl. ..H0lg 9/10 minal member oftheseal, whether glass to metal or ceramic to [58] Fleld of Search..3l7/230, 23L 233, 234; metal, may include a metal selected from thelow-carbon 174/525, 50-61 steels, the Group I metals (copper, silver andgold, or alloys thereof or clad materials thereof), the Group Vlllmetals [56] Reterences cued (nickel, palladium and platinum or alloysthereof or clad UNITED STATES PATENTS materials thereof),lron-nickel-cobalt alloys or clad materials thereof, nickel-iron alloysor clad materials thereof, chromi- 2,210,699 8/1940 Bahls ..174/50.6l Xum-iron alloys or clad materials thereof or a metal from any 3,275,3589/1966 Shoneberger.. ..37/230 X one of the film-forming metals which canform an electrolytic 3, 1966 rafi 317/230 X oxide film such as tantalum,aluminum, niobium, titanium, zir- 5, 9/1966 Merritt 8t a m- /230 coniumalloys thereof or clad materials thereof. The glass 3,336,433 8/ 1967Johnson et member may include any one of the borosilicate, potash-soda-3,489,845 1/1970 Landfon barium, potash-soda-lead,' soda-lime oraluminia-silicate 2,776,467 1/1957 Brennan" 317/230 X glasses. Theceramic member may include any one of alumina,

Fuller "3 Steatite fosterite or beryllia 2,923,866 2/1960 Wagner 317/230I 3,268,778 8/1966 Worsham ..3l7/234 33 Claims, 9 Drawing FiguresPAIENIEUFEB 29 m2 SHEET 1 BF 2 INVENTORS m 6 Mn N L R LEL o ASL/fr. w mT O .A w w RJ.L O D ENR GHA JFJHIR} 5 PAIENIEDFEB29 I972 SHEET 2 [IF 2 F9 lNVENTORS GEORGE WALLIS JOHN J. DORSEY BER RD L. PHILLIPS C MMATTORNEY rmruvnmc SEAL The presentinvention relates to an insulator tometal her- .metic seal, for .electronic components, andmorepai'ticularly, to a .miniature'glass tometal andceramic to metalseal and methodsof-makingthe same.

for example;.the seal should be hermetic over a wide range oftemperatures; the seal should be resistant to corrosive action of .acidelectrolyteswhere it is used .to electrolyte capacitors =having..an:acidelectrolyte, and the seal should possess mechanical-propertiessufiicient to withstand-adverse condi- ,tions suchzas shock,vibration.and the like..The. glass or ceramic- .portion 101': member ofthe hermetic sealshould have high .dielectricrstrength :highevolumeresistivity, high-surface resistivityand low-power factorand lossfactor.

Prior artglass to'metal hermetic seals maybe categorized into twogeneral types of hermetic seals, that is, matched seals and unmatched.seals. ln matched hermetic seals, the coefficientof thermal expansion ofthe glass or the ceramic material correspondsclosely to that of themetal members. In addition,

the hermetic. seal .depends on adherence between the glass or theceramic member and the metallic member to-provide. a hermeticsealtherebetween. The maximum tolerable difference between the coefficientof expansion of each of the members of theseal is usually about l0' l C.

Matched xheremetic seals employ glasses which areespecially mixed sothat the coefficient of thermal expansion of the glass membercorresponds'closely to that of the metal member towhich the glass memberis to be fused. Whatever the metal member or. theglass memberemployed inthe matched hermeticseal; the joint between the members of the hermeticseal depends on adherence or fusion between molten glass r'nemberand themetal member Generally, the metal member includes'a-preformed oxide filmon the surface thereof or the metal memberand the glass are heated orfired in an oxidizing atmosphere so that an oxide coating is forked onthe surface of the metal member during the fabrication of the hermeticseal, or'the metal is treated in some manner to promote adhesion betweenthe glass and the metal. Generally, molten glass possesses'a highaffinity for metal oxides in that the metal oxides are readily wettedbythe glass to thereby provide a glass to metal hermetic seal whereinthe glass member is fused to the metal member. 7

Perhaps. the most common of matched hemietic seals employ nickel-ironalloys such as alloy sold under the trade name KOVAR. The nickel-ironalloys generally possess coefficients of vthermal expansionsubstantiallyithe same as that of a borosilicateglass soldby the ComingGlass Company as '7,052. One'of:the steps generally performed in makingmatched hermetic seals using KOVAR metal members is that of forming anoxide film on the KOVAR metal members prior to fusing the KOVAR metalmembers'to the Coming 7,052 glass bymelting the glasso'lhe thickness ofthe oxide film on the KOVAR metal membersappearsto be important for toolittle or too much oxide film may result in a seal which may not behermetic or in a seal which may have other undesirable characteristics.The oxide film of the surface of the KOVAR metal members is dissolved orinterlockedwithconstituents, such as, boric oxide and silica, of themolten glass. The oxide film on the KOVAR metal members appears to bethe means by. which a fused joint between the-KOVAR members and theglass member of the matched hermetic seal is provided.

Compression-hermetic seals, on the other hand,'are based on theelasticity of theglass member and stresses formed in the glass memberdue to'the differences in coefficient of thermal expansion of themetalmember andthe glass member. It

should be seen that compression hermeticsealsgenerally do not'dependupon adherence or, fusion between the glms and the metal member.

in fabricating glass to film-forming metal hermetic seals for use inelectrolytic capacitors having'an acid electrolyte, it is important thatthe terminal member be substantially inert to the corrosive'action ofthe acid electrolyte or have the property of forming an electrolyticoxide. on the exposed surface thereof which is substann'ally inert tothe corrosive action of the acid electrolyte. If the hermetic seal is tobe used in an acid electrolyte environment,- the thermal coefficientofexpansion and the chemical inertness of the metal member are of primaryconsideration. The electrolytic oxide formed on the surface of afilm-forming metal where tantalum is used as the terminal member is an.amorphous dielectric oxide film. The tantalum oxide film is generally asubstantially unifonn, thin layer of tantalum pentoxideelectrochemically formed on the surface of the tantalum terminal member.Ifan electrolytic oxide film does not substantially, cover the surfaceof the film-forming terminal member, the hermeticseahwhen placed intheacid electrolyte environment, will exhibit high-electrical leakage,poor equivalent series resistance, poor voltage characteristics and thelike. If the tantalum terminal has any substantial amount ofcrystalline, thermally grown tantalum pentoxide on its surface, it isvery difficult to form an electrolytic oxide on the surface of thetantalum terminal.

Conventionally fabricated hermetic seals generally include a metaleyelet, a terminal means which projects through the aperture of theeyelet and a mass of glass which substantially completely fills theaperture of the eyelet and retains the terminal wire spaced from theeyelet. The geometry of the conventional hermetic seal is such that itis difficult to reduce the geometry of the hermetic seal to much lessthan a thickness of about mils and a diameter of about [00 mils. Thelimitation on the dimensions of the seal limits the size to which theelectronic component such as a capacitor may be reduced.

Accordingly, it is an object .of .the present invention to provide ahermetic seal for an electronic component which overcomes the problemsof the prior art.

metic seal for an electronic component which has a novel construction.

Another object of the present invention is to provide a hermetic sealfor an electronic component which has a geometry having a thickness ofabout 25 mils and a diameter of about 60 mils.

Yet another object of the present invention is to provide a hermeticseal for an electronic component wherein the thermal coefficient ofexpansion of an insulative member is substantially the same as thethermal coefficient of expansion of a metallic member or members of thehermetic seal.

A further object of the present invention is to provide a hermetic sealfor an electronic component including an insulative member having nomeniscus.

Yet another, object of the present invention is to provide a hermeticseal for an electronic component which does not rely on internalstresses developed within an insulative member to provide-a hermeticseal.

Yet still another object of the present invention is to provide ahermetic seal for an electronic component which is substantially leakproof. I

Another object of the present invention is to provide a hermetic sealincluding an insulative-membersuch as glass or a ceramic material bondedto a metalumember using a process whereby the insulative rriemberis notrendered molten during trolytically anodized.

A further object of the present invention is to provide a method ofmaking a hermetic seal for an electronic component which is inexpensiveto manufacture.

Another object of the present invention is to provide a method of makinga hermetic seal for an electronic component including a ceramic or glassmember bonded to a metal member by an electrostatic attractive force.

Yet another object of the present invention is to provide a ceramictometal or glass to metal seal for electronic components which issubstantially leak proof throughout its useful life.

Yet another object of the present invention is to provide anelectrolytic capacitor including a ceramic to metal or glass to metalhermetic seal.

Other objects of the invention and the nature thereof will becomeapparent from the following description considered in conjunction withthe accompanying drawing. The dimensions of the members of the hermeticseal are exaggerated with respect to one another to better illustratethe concepts of the present invention.

FIG. 1 is an enlarged perspective view of the insulator to metal seal ofthe present invention;

FIG. 2 is an enlarged cross-sectional side view of the insulator tometal seal shown in FIG. 1;

FIG. 3 is an enlarged cross-sectional side view of an insulator to metalseal illustrating one end of the insulator member substantially coveredwith a fired on paint of a solderable metal;

FIG. 4 is an enlarged cross-sectional side view of an electrolyticcapacitor using the insulator to metal seal of the present invention toclose the open end of a container;

fig. 5 is an enlarged cross-sectional side view of an electroniccomponent using the insulator to metal seal of the present invention toclose the open end of a container;

FIG. 6 is an enlarged cross-sectional side view of a semiconductordevice using the insulator to metal seal of the present invention toclose the open end of a container;

FIG. 7 is an enlarged perspective view of a plurality of insulator tometal seals of the present invention;

FIG. 8 is an enlarged cross-sectional side view of the plurality ofinsulator to metal seals illustrated in FIG. 7; and

FIG. 9 is a schematic illustration of equipment used to bond aninsulator to metal by the application of an electric potential producingthe passage of current to the insulator and the metal.

Generally speaking, the present invention relates, in its broadestaspect, to an article of manufacture including an apertured electricallyinsulative member, a metal member sealed to and closing one end of theapertured insulative member and an elongated strip of metal attached tothe metal member and projecting outwardly from the metal member into theaperture of the insulative member and methods of making the same. Thearticle of manufacture may be used to hermetically seal electroniccomponents such as semiconductors, integrated circuits, energy cells,resistors, capacitors and the like.

Referring to the drawing, FIGS. 1 and 2 illustrate an insulator to metalhermetic seal 10 of the present invention, Theinsulator to metalhermetic seal 10 includes a terminal member 11 which comprises a metalplate or disc 12 and a metal electrode l3 fixedly attached to the plateby any suitable means such as by welding or the like. For purposes ofillustration and not for purposes of limitation, the metal plate 12 mayhave a diameter of about 50 mils and a thickness of about 10 mils. Themetal electrode may have a diameter of about 5 mils. It should be seenthat the diameter of the metal plate is governed primarily by thediameter of the open end of a container 30, such as shown in FIG. 4,which the hermetic seal is intended to close and by the interface area17 between adjacent surfaces of insulator ring 14 and the metal plate 12necessary to effect a satisfactory hermetic bond, which is about 20 milsin width. The insulative ring I4 may be fabricated from any suitableelectrically insulative material such as glass, ceramic material or thelike and is bonded to the metal plate 12 by processes to be discussedhereinlater. The insulative ring may have a thickness of about 5 mils ormore. The insulative ring may have an outside diameter about the same asthe diameter of the metal plate, that is, about 50 mils, and an axialaperture 15 having a diameter of, for example, about 10 mils. Anexternal metal terminal member (not shown) may be attached to the metalplate on the surface opposite the surface of the metal plate to whichelectrode 13 is attached. The insulative ring 14 may be bonded to ametal ring 16 as shown in FIG. 2. The thickness of metal ring 16 isabout 10 mils. It is seen that the thickness of a hermetic sealincluding metal plate 12, insulative ring 14 and metal ring 16 is about25 mils whereas the diameter of the seal may be about 50 mils which isconsiderably smaller in size than the size of the conventional insulatorto metal seal.

The metal plate 12 member may be fabricated from any suitable metal suchas a low-carbon steel having good machinability characteristics. Thefollowing examples of materials which may be used in the seal structureare given as weight percents. A suitable low-carbon steel may be SAE1010 steel which contains about 0.08 percent to about 0.13 percentcarbon, about 0.30 percent to about 0.6 percent manganese, up to about0.04 percent phosphorous, up to about 0.05 percent silicon, theremainder essentially iron; wrought, free-cutting steels such asAlSl-types B 1,112 or B 1,1 13 which contain up to about 0.13 percentcarbon, about 0.6 percent to about 1 percent manganese, up to about 0.12percent phosphorous and up to about 0.33 percent silicon, the remainderessentially iron. The thermal coefficient of expansion of SAE 1,010steel is about 84Xl0"' C. and the thermal coefficient of expansion ofB1,112 and B 1,113 is about 84 l0"'/ C. In addition, the metal of themetal plate 12 may be selected from the Group I metals such as copper,silver and gold, alloys thereof or clad materials thereof and the like;the Group II metals such as nickel, palladium, platinum, alloys thereofor clad materials thereof and the like; or any of the film-formingmetals such as tantalum, .niobium, aluminum, titanium or zirconiumalloys thereof or clad materials thereof and the like; iron-nickelcobaltalloys or clad materials thereof and the like; nickel-iron alloys orclad materials thereof and the like; and chromiumiron alloys or cladmaterials thereof and the like.

Where the thermal coefficient of a particular metal to be used for theplate member 12 exceeds a thermalcoefficient of expansion of about100X10"/ C., such as'for example aluminum, nickel, palladium, copper,gold and silver which have thermal coefficients of expansion of about257 l0" C., about 133x l0- C., 1 17X lO"/ C., 178x l0-/ C., l43 l0 C.,and 206 10" C. respectively, the metal having a high thermal coefficientof expansion maybe used to clad a base.

metal or base metal alloy so as to reduce the effective thermalcoeflicient of expansion of a metal such as aluminum, nickel and thelike to l00 l0 C., or'less. Forexample, a 10 mil thick piece of aniron-nickel alloy sold under the trade name KOVAR may be used as a basemetal and may be clad with a 1 mil thick piece of aluminum. The aluminumclad KOVAR appears to possess an effective coefficient of thermalexpansion similar to that of KOVAR, that is, the aluminum clad KOVARappears to have a thermal coefficient of expansion of about Q l( /f I.jThus, the metal having a coefficient of thermal expansion may be usedto clad a base metal and the resultant clad material may have acoefficient of thermal expansion similar to that of the base metal.

If the hermetic seal of the present invention is to be used tohermetically seal electronic components in general, SAE 1010 steel andnickel-iron alloys, the nickel-iron alloys sold under the trade nameKOVAR is most preferred. KOVAR may contain about 28.7 percent toabout29.2 percent nickel, about 17.3 to about 17.8 percent cobalt, up toabout 0.5 percent manganese up to about 0.2 percent silicon, up to about0.06 percent carbon, the balance essentially iron.

If the nickel-iron alloy sold under the trade name KOVAR is used as thematerial for the metal plate l2, the glass or ceramie material ofthehermetic seal should have a thermal coefficient of expansion withinabout 20+l07/ C. of the metal of the metal plate 12 to. provide amatched, hermetic seal. The thermal coefficient of expansion of KOVAR isabout 50x10- metal seal. The existence of either one of or both of theconditions may harmfully effect the operation of the liquid electrolytecapacitor. Therefore, in an electrolytic capacitor having a tantalumanode and a sulfuric acid electrolyte, the metals 'P C. Suitable glasseswhich may have thermal coefficient of 5 of the container and the sealshould be tantalum or a metal expansion similar to that of KOVAR are theborosilicate glasseswhich usually contain up to about 80 percent silica(SiOy), up to about 14 percent boric acid (3,0,), up to about 4; percentsoda (Na,0), the remainder essentially alumina fAhO Typical borosilicateglasses which may be used as the glass-member of the seal may be 7.040,7.050, 7,052, 7,055 and 7,056 sold by the Coming Glass Company, havingthermal coefficients of expansion of about 48 l0"/ C. about 46x10 0.,about 46Xl0"/ C., about 5l.5Xl0 C., and about 5 1X 10*! C. respectively.Typical borosilicate glasses soldby.

theyMansol Ceramics Company which may be. as the glass member of theseal may be 02-000, 15-000, 33-000, 37-000 and 50-000 having thermalcoefficients of expansion of about 46X l"/ C., about 51.5Xl0"/ C., about46 10 C., about l'Xl0"'/ C., and about 48Xl0/ C. respectively. 0ftheseveralborosilicateglasses, Corning 7,052 and 7,056 or M80801 02000are preferred when the metal plate 12 is fabricated from KOVAR.

The metal of the electrode 13 may be the same as the plate ora differentmetal. It is preferred, however, that the metal of theelectrode besubstantially the same as the metal of the plate member.

A ceramic material such as alumina (A1 03) steatite (H MgASiO L),fosterite (Mg,SiO.,) and beryllia (8&0) having thermal coefficients ofexpansion of about 64Xl0 l C., about 69XXl0"'/ 0., about moxie-U" C.,and about 60x10- C., respectively, may be substituted for the glassmaterial in the hermetic seal. When KOVAR is used as the metal for theplate member, alumina or beryllia are preferred with beryllia being the.most preferred insulator material. It is to be understood that theother ceramic materials may be preferred over alumina or beryllia if themetal of the plate member is, for example, palladium or a palladium cladmaterial havinga thermalcoefficient of expansion of about 89 l0' C.Where palladium or palladium clad material is used for the metal of theplate member 12, fosterite having a thermal coefficient of expansion ofabout l00Xl0 C. would be preferred over alumina and beryllia.

FIG. 4 shows the insulator to metal seal of the present in- 45 ventionused to close the open end of a container 30 which serves as the housingfor an electronic component such as capacitor body 31. The capacitorbody may be an anode fabricatedfrom a film-forming metal such astantalum, aluminum, niobium, titanium, zirconium and the like having amyriad of intercommunicating voids. A solid electrolyte of manganesedioxide (MnO or the like may be used as the electrolyte of thecapacitor. The use of a solid electrolyte such as manganese dioxide .maypermit the use of nearly any one of the..,above-mentioned combinationsof metal members and glass or-ceramic members to provide the insulatorto metal hermetic seal. The open end of the container 30 is closed byattaching the metal ring 16 of the insulator to metal hermetic seal. toan annular shoulder of flange 32 of the container by any suitable means;such as by welding, soldering and the like as shown at 17 in FIG. 4.

Where the capacitor body 31 is substantially immersed in an acidelectrolyte such as sulfuric acid, acetic acid, lithium chloride and thelike, the metal materials of the capacitor such as the container 30,theplate 12 and the electrode 13 should be. of the samefilm-formingmetal or the container andthe plate should be. fabricated from amaterial chemically inert to the corrosive action of the acidelectrolyte in order to minimize, the occurrence of galvanic corrosionwithin the capacitor housing. Detrimental galvanic corrosion may occurbetween dissimilar metals in the acid electrolyte environment present inacapacitor using an acid electrolyte. The galvanic corrosion may lead tohigh-leakage currents and/or deterioration of the joint betweenthecontainer and the insulator to l mal coefficient of expansion ofabout 73Xl0"/ C. A suitable which is substantially inert with respect tothe acid electrolyte such as silver, gold, platinum,.palladium, alloysthereof such as a silver l0 percent gold alloy and materials clad withsilver, gold, platinum, palladium such as stainless steel clad with 10silver having a thickness of at least 1 mil or stainless steel cladwithgold havingathicknessofatleast l milorstainlessteel clad with analloy ofsilver 10 percent gold having a thickness ofat least mil and thelike. Of'the severalpossible metal materials which may be used-astheoontainer materialand the metal portion of the hermetic seal of anacidelectrolyte tantalum capacitor, it is preferred that the metalmembers of the hermetic seal be fabricated'frorn tantalum or stainlessteel clad with an alloy of silver- 10 percent gold with tantalum 0being the most preferred material. Where tantalum is used as the metalof the plate member 12, the glass or ceramic ring should have a thermalcoefiicient of expansion which approximates the thermal coefficient ofexpansion of tantalum. Tantalum has a thermal coefficient of expansionof about 65 X10 46 -l0'-- /.".C.,.is-prefefred.- Suitable ceramicmaterials for. the

insulator portion of the hermetic seal would be steatite, aluminaandberyllia with alumina and beryllia being preferred with alumina beingthe most preferred ceramic material.

Where niobium is used as the film-forming metal of the capacitor anodeof the capacitor 31 and the electrolyte is 1 an acid electrolyte such assulfuric acid or the like, the metal 2 members of the hermetic sealshould be niobium or a metal or clad material which is chemically inertto the acid electrolyte in order to minimize galvanic corrosion. Niobiumhas a therglass may be Corning 6,810 which has a thermal coefficient ofexpansion of about 69Xl0"/ C. A suitable ceramic material for theinsulator portion of the hermetic seal may be steatite, alumina andberyllia with steatite being the most preferred ssrepismsteis V. V

Where gold is used for the plate member 12 in an electrolytic capacitorhaving an acid electrolyte and the capacitor body is an anode offilm-forming metal fabricated from tan- 50- talum, niobium and the like,a suitable glass may be any of the potash-soda-lead glasses such 1,990sold by the Coming Glass Company having coefficient of expansion'ofabout l24X10"'/ C. A suitable ceramic materialmay be fosterite having acoefficient of thermal expansion of about l00Xl0"/ C. The coeftheeffective coefficient of expansion of gold may be reduced 25 C. Suitableglasses would be Corning Glasses 7,040, 7,050,

ficient of expansion of gold-is about l42 l0""/ C., however,

by providing a base metal clad with gold which may have athcrmalcoefficient of expansion similar to that of the base mode .7

Where platinum is used for the plate member 12 in an electrolyticcapacitor having an acid electrolyte and a capacitor body 31 isfabricated from tantalum, niobium and the like, a suitable glass for theinsulator portion of the insulator to metal C., and thepotash-soda-bariu m glasses such u'clirfiing 9,010-

seal may beany of the soda-barium glasses such as Corning C., withComing 9,010 pbtash-soda-barium glass being the most preferred glass foruse with platinum. The thermal coefficient of expansion of platinum isabout 89Xl0 C. A suitable ceramic material for the insulator portion ofthe hermetic seal maybe steatite and alumina with steatite being themost.

preferredceramicmaterial.

It should be seen that any of the ceramic materials, alumina, steatite,fosterite, or beryllia may be substituted for any of the glassesmentioned above as long as the thermal coefficient of expansion of theceramic material approximates that of the metal material so as toprovide a matched hermetic seal.

Referring now to FIG. 3, an embodiment of the insulator to metal seal 10is illustrated. The seal 10 includes a terminal member 11 whichcomprises a metal plate 12 and a metal electrode fixedly attached to theplate by any-suitable means such as by welding or the like. A solderablemetal is .painted onto the insulator member in lieu of bonding the metalring 16 to the insulator member. A suitable solderable metal may beprovided by a paint containing platinum and gold manufactured by DuPontas 7,553 or 8,236. The solderable metal is painted onto surface 22 ofthe insulator material sufficiently thick to provide a metal coating atleast about 1 mil thick after firing the paint to bond it to theinsulator material. The platinum and gold is placed on surface 22 of theinsulator by any suitable process such as by a silk screening technique.The paint is fired at about 700 C. to about 900 C. for about 15 to 30minutes.

P16. 5 shows a hollow, cylindrical container 30' having its open endclosed by insulator to glass seal 10 having metal ring 16' attached tothe inner wall of the cylindrical container by any suitable means suchas by welding, soldering and the like as shown at 41.

I Referring now to FIG. 6, a semiconductor device 50 is shown. Asemiconductor wafer 51, fabricated from any suitathe flat extremity ofthe housing and also serves to electrically connect the wafer to thecup-shaped housing. An electrically conductive electrode 13 is afiixedto the major surface of the wafer thereby forming a contact. The outersurface of the flat extremity of the cup-shaped housing may serve as theother conductive lead (not shown) may be soldered to the outer extremityof the cup-shaped housing. The wafer 51 is substantially completelycovered by any suitable insulative material such as epoxy resin 56 orthe like. The epoxy resin coating over the wafer serves to protect thewafer from humidity, dust or other like contaminates. The epoxy resinalso serves to protect the wafer from shock and vibration. The housingis fabricated from any suitable heat conductive and resilient materialsuch as aluminum, copper and the like. The insulator to metal hermeticseal 12 is attached to the circular flange 57 of the housing 52 tothereby hermetically seal the semiconductor device.

It should be noted that no meniscus exists between the glass and thespaced apart metal members 12 and 16 or 16', that is, the externalsurface of the glass is not a crescent-shaped surface which is eitherconcaved such as exists when the glass wets the metal members 12 and 16or 16' or convex such as exists when the liquid does not wet the metalmembers 12 and 16 or 16'. The lack of meniscus may be due in part to theuse of an electrostatic bonding process to bond the glass to the metalmembers. 1

The method of bonding the insulative member such as the glass memberor-the ceramic member to the metal member of the insulator metal sealmay be accomplished in several ways.

vided with input terminals 83 and 84 for connection to a suitable powersource such as an AC source (not shown). The platen or the glass membermay be heated by any of several different methods other than thesuggested resistance heating method. For example, the platen may beheated by a gas flame or by a suitable induction heating technique. Itmay be possible to heat the glass member directly as in a furnace (notshown) thereby eliminating the use of the platen 80.

A suitable power source such as, for example, a direct current powersource 85 including an output terminal 87 connected to platen 80 andanother output terminal 86 connected to the KOVAR member 90. The powersource may be a direct current power source, a pulsating direct currentpower source or in some instances, an alternating current power source.The power source has its output terminals 86 and 87 connected to theKOVAR member 90 and the glass member 81 through the platen respectively.The terminals 86 is shown as being connected to the KOVAR member througha resilient contact such as a spring contact 89 which is in directcontact with the KOVAR member. Output terminal 87 of the power source isconnected to an input terminal 88 of the platen and through said platento the glass member 81.

In the practice of the present invention, the KOVAR member and glassmember are placed in close contact as shown in FIG. 9 and the glassmember is heated to a temperature below its softening point through theplaten. The softening point of Coming 7,052 glass is about 710 C. andthe working point is about l,130 C. An electrical potential provided bythe power source is applied cross the juxtaposed metal and glass membersforming a bond at the interface 91 between the KOVAR member and theglass member. The bond between the glass and the metal member isbelieved to be formed by the electrostatic attractive force generatedwhen a potential applied across the juxtaposed metal and glass membersis suf- The preferred temperature to which theglass member is Apreferred method of bonding the insulator member to the soda (Na,0), upto about 3 percent potash (K 0), and the heated will vary dependent-onthe type of glass, but generally will be in the range of about 150 C. toabout l,000 C. For a variety of borosilicate glasses, the temperaturepreferably is in the range of about 300 to 700 C', for soft glasses suchas soda-lime glasses, the range is about l50 to 400 C., and for quartzglasses the temperature may vary from about 600 C. to about l,000 C. Theapplied voltage and the current density may vary within wide ranges forit is thought that neither value is critical. In general, the potentialis usually in the range of about 200 to about 2,000 volts. Adefmitevalue for the current density cannot be established particularlysince, if the applied potential is maintained constant, the currentgradually decreases from, for example, a value in the range of about toabout 300 or more microamperes/cm. toapproximately 0 as the bondprogresses from its starting point to the edges of the juxtaposedmembers. The higher the potential and the corresponding current the lesstime required to effect electrostatic bonding between the juxtaposedmembers. The upper limit of the potential and the current density isthat disruptive discharging should not be permitted to occur between theglass member and the metal member.

Another factor involved iii bonding KOVAR to glass using theelectrostatic bonding process is the surface finish and the flatnem ofthe two surfaces of the bonding interface. Good bonds may be obtainedmore easily when the surfaces are substantially smooth. Polishing of theinterface surfaces appears to provide a better bond between the glassmember and the metal member.

The type of power source, and in the case of direct current, thepolarity is applied to the glass member and, the metal member may dependin some instances on the type of glass being used to provide theinsulator portion of the hermetic seal. For example, the distributioncharacteristics. of the glass whether symmetrical or asymmetricaldetermine,it is thought,

cal borosilicate glass. Corning glass 7,059 is another example ofasymmetrical glass. For optimum bonding results where the insulator 81is 7,052, the terminal 88 should be made negative. If the glass usedshould be asymmetrical but in the opposite direction from the glass7,052 then the terminal 88 should be connectedto the positive side ofthe power source 15.

If the glass being bonded to KOVAR has substantiallysymmetricakpotential distribution as is the case of Coming 7,059 glass,the polarity of the applied potential and the direction of current'flowthrough the KOVAR in the glass is not of any importanceThat is, eitherpositive or negative direct current or pulsating direct current oralternating current will bonding'if the glass has symmetrical potentialdistribution.

In a specific example of bonding glass to KOVAR, the glass Corning 7,052having a thickness of about mils is heated to a temperature in the.range of about 500 C. to about 550 C. and a'di rect current power sourcewas applied across the glass and the KOVAR member with the glass andKOVAR in contact in a manner generally illustrated in FIG. 9. Thenegative output terminal of the power source is connected to the glass.A potential of about 800 to about 1,000 volts was applied for a shortperiod of time in the range of l to 3 minutes or more causing a currentflow from the KOVAR to the glass and a satisfactory hermetic bond iseffected.

It maybe noted that a lack of meniscus may be observed in the insulator.to 'metal seal fabricated by the electrostatic bonding process. The lackof meniscus may be due in part to the steps followed during the process.

. Alternatively, the insulator to metal seal 10 shown in FIGS. 1, 2, 3and 4 may be fabricated by stacking the metal washer and apreformedinsulator ring 14 onthe metal plate 2. Assuming the metal plateand the metal washer are a film-forming metal such as tantalum and theinsulator ring material is a borosilicate glass such as Corning 7,052,the stacked array may be heated inany suitable furnace such as aninduction heating furnace under a pressure of about 1 atmosphere in aninert atmosphere such asflowing argon at a temperature above the workingpoint temperature of the glass, which for Corning 7,052 borosilicateglass is about 1,130 C. The stacked array .may be heated to about l,100C. to about 1,200" C. for about to about 30 minutes. The insulator toglass seal-is cooled to room temperature under argon. The seal maybefiredunder reduced pressure or in a vacuum. Firing the seal inaninertglass atmosphere substantially prevents the formation ofthermally growntantalum pentoxide, which, may provide a surface on whichit is difficult to form an electrolytic oxide film. 1

The process immediately above may'also be used to provide heated in anoxidizing atmosphere such as air rather than in an inert atmosphere.

Another method of making the insulator to metal seal 10 shown in FIGS.1, 2, 3 and 4 is by stacking the metal washer and a preformed insulatorring 14 on the metal plate 12. As suming the metal plate and the metalwasher are each stainless steel clad with about 1 to 3 mils of an alloyof silverl0 percent gold and the insulator ring material ispotaslrsoda-barium glass such as Corning 9,010, the stacked array may beheated in any suitable furnace such as an induction heating furnaceunder a pressure of about 1 atmosphere in an inert atmosphere such asflowing argon at a temperature of about 930 C. to about 950 C. for about20 to about 30 minutes. The temperature to which the glass is heated isabove the softening point temperature of the glass and below the workingpoint temperature of the glass. The insulator to glass seal is cooled toroom temperature under argon. The seal may be fired under reducedpressure or in a vacuum.

Yet another method of providing the insulator to metal seal is to stackthe metal washer, the preformed insulator and'the metal plate in asuitable press such as a jig. A moderate amount of pressure, that isabout 25 lbs. per sq. inch, may be provided. Assuming the metal plateand the metal washer are a film-forming metal such as tantalum and theinsulator ring material is a borosilicate glass such as Coming 7,052,the stacked array may be heated in any suitable furnace such as aninduction heating furnace under a pressure of about 1 atmosphere such asflowing argon at a temperature above the softening point temperature ofthe glass but below the working point temperature of the glass. Thearray may be heated-to about 700 C. to about 750 C. for about 20 toabout 30 minutes under a pressure of about 25 p.s.i. applied by the jig.The insulator to glass seal is cooled to room temperature under argonThe seal may be fired under reduced pressure or in a vacuum. Firing theseal in an inert glass atmosphere substantially prevents the formationof thermally grown tantalum pentoxide, which, provides surface on whichit is difiicult to form an electrolytic oxide film.

The ceramic insulator materials, that is, alumina (A1 0 steatite(H,Mg;,(SiO fosterite (Mg,SiO,) and beryllia (BeO), may be bonded to themetal plate 12 and/or to the metal ring 16 or 16' by metallization andbrazing of the'ceramic material thereto. The metal may be'applied to theceramic surface by painting, vapor deposition, flame spraying and thelike. Some metals adhere to someceramic surfaces with little or nospecial-surface preparation. Whether by direct wetting or by specialformation of a transition layer, the bond is satisfactory. Coatings ofsilver, copper, gold, platinum, iron,

cobaltand nickel may be used with the noble metals silver,

gold and platinum being preferred and with a silver being the mostpreferred of the noble metals. A silver layer may be applied to theceramic material by chemical reduction, by dusting or by painting. Thenoble metals are usually painted; Unlike silver coatings, platinumcoating may not require firing prior to being brazed. Silver paint maybe applied by anycmiventional silk screening process and thereafterheated to a temperature of about 700 C. to about 900 C. for 15 to 30minutes. A suitable silver paint includes silver flake about 45 percent,lead borosilicate about 2.5 percent, alkydresin about 4.5 percent andbutylalcohol-xylene-toluene about 48 percent. A suitable platinum paintincludes platinum powder about 40 percent, mercuric chloride about 10percent, lead borosilicate about 3.5 percent, anthracene about 2.5percent and a plasticized resin medium about 44 percent. A suitablecobalt paint contains cobalt powder flux, cellulose nitrate and amyllactate and is fired in a suitable reducing atmosphere such as argon atabout l,350 C. to about 1450 C.

Fired-on silver films may be timed before brazing, however, if thesilver surface is maintained too hot too long, either'in timing orbrazing,.substantially allthe silver may dissolveunless previouslycoated with a barrier layer. Therefore, the'ini tial layer may be builtup with an electroplate or sprayed-on deposit of nickelor copper.

The metallization of the ceramic material may be accomplished by vapordepositing chromium, titanium, silicon films and the like. The films maybe deposited by spraying volatile metal chlorides in hydrogen onto theceramic material from burner nozzles. The gaseous metal chlorides andthe hydrogen react to provide the metal on the surface to be metallized.The hot hydrogen chloride reaction product serves to blanket the surfaceand inhibit oxidation. Molybdenum, tungsten, and tantalum films may beformed by hydrogen reduction of volatile metal chlorides. Iron, nickel,and cobalt films may be deposited by decomposition of volatile metalcarbonyls.

Flame spraying may also be used to provide a bonded metal coating onceramic materials. Mixtures of tungsten carbide, powers and iron, nickelor cobalt may be flame sprayed onto the ceramic material.

An example of bonding steatite to KOVAR is as follows, Steatite may besubjected to successive molybednum-iron and nickel coatings with theKOVAR being copper flashed. A small piece of silver is placed betweenthe two materials and the assembly is fired at about l,000 C. to providea seal including steatite bonded to KOVAR.

FIGS. 7 and 8 illustrate a plurality of insulator to metal seals 10. Theplurality of seals may be used to provide external terminal for anelectronic component such as an integrated circuit. A metal sheet 60fabricated from any of the metals discussed hereinbefore and a sheet 61of insulative material are provided with a multiplicity of matchingapertures 62 and 63 respectively, A geometrical configuration 64 asshown in FIG. 7 includes plates 12' interconnected by reduced portionsor necks 65. The members are sealed to each other using any one of themethods described hereinbefore. The necks may be removed by any suitableprocess to provide the structure of FIG. 8. A suitable process may bedepositing a suitable wax or resist over the plates 12' and then usingan etching process to remove the reduced neck portions 65.

While the invention is illustrated and described in an embodiment, itwill be understood that modifications and variations may be affectedwithout departing from the scope of the novel concepts of this inventionand as set forth in the appended claims.

' Having thus described our invention, we claim:

1. An article of manufacture comprising:

an electrical component within a container therefore, said containerhaving at least one opening therein;

said electrical component having an electrically conductive lead memberin electrical contact with said component; a seal member closing saidopening in said container; said seal comprising; i an insulative memberof glass or ceramic material having an aperture therein; said insulativemember being integrally bonded to a first metal member along a firstband interface, said first metal member having an aperture therein; saidinsulative member also being integrally bonded to a second metal memberalong a second bond interface, said second bond interface beingsubstantially parallel to said first bond interface, said second memberclosing the aperture in said insulative member; said lead member passingthrough the aperture in said first metal member and through the aperturein said insulative member and into mechanical engagement with saidsecond metal member;

said insulative member being elongated in a direction substantiallyparallel to said first and second bond interfaces. 2. The article asclaimed in claim 1, wherein said metal member is selected from the groupof low-carbon steels,

. Group I metals or alloys or clad metals thereof, Group VIII soda-limeglasses or alumina-silicate glasses.

4. The article as claimed in claim 3, wherein said glass is aborosilicate glass.

5. The article as claimed in claim 2, wherein said insulator member is aceramic material selected from the group of alumina, steatite, fosteriteand beryllia.

6. The article as claimed in claim 2, wherein said Group I metals arecopper, silver or gold, said Group VIII metals are. I

nickel, palladium or platinum and said film-forming metals are tantalum,aluminum, niobium, titanium or zirconium.

7. The article as claimed in claim 1, wherein said insulative member isborosilicate glass or alumina and said metal member and said elongatedmetal strip of metal are tantalum or a nickel-iron alloy or asilver-gold alloy.

8. The article as claimed in claim 7, wherein said metal member and saidelongated strip of metal are tantalum.

.9. The article as claimed in claim 7, wherein said metal member andsaid elongated metal strip are a nickel-ironalloy including up to about30 weight percent nickel, up to about 18 weight percent cobalt, tracesof manganese and silicon and carbon, the remainder essentially iron.

10. The article as claimed in claim 7, wherein said metal member andsaid elongated metal strip are a silver-gold alloy including up to about90 percent silver, the remainder essentially gold.

11. An article according to claim 1 wherein said article is a capacitorand said component is at least in part a capacitor anode. I

12. A capacitor according to claim 11 which is an electrolyticcapacitor.

13. An article according to claim 1 wherein said seal member is ahermetic seal.

14. The hermetic seal of claim 13, wherein said aperture of saidinsulator member is about 10 mils or more and said insulator memberhaving a length and a width of about 50 mils or more, said metal memberclosing said one end of said apertured insulative member having a lengthand a width of about 50 mils or more, and said aperture of saidapertured metal member having a diameter of about 10 mils or more andhaving a length and width of about 50 mils or more.

15. The hermetic seal of claim 14, wherein said elongated strip of metalis spaced from the inner wall of said aperture of said insulative memberand from the inner wall of said apertured metal member.

16. The hermetic seal of claim 15, wherein said elongated metal strip isa metal wire having a diameter of about 5 mils or more.

17. The hermetic seal of claim 16, wherein the thickness of saidinsulative member is about 5 mils or more, the thickness of said metalmember closing said one end of saidapertured insulative member is aboutl0 mils or more and the thickness of said apertured metal member isabout 1 mil or'more.

18. The hermetic seal of claim 17, wherein said thickness of saidapertured metal member is about 10 mils or more.

19. The article as claimed in claim 17, wherein said metal member isselected from the group of low-carbon steels, Group I metals or alloysor clad metals thereof, Group VIII metals or alloys or clad metalsthereof, film-forming metals or alloys or clad metals thereof,iron-nickel alloys or clad metals thereof or chromium-iron alloys orclad materials thereof.

20. The article as claimed in claim 17, wherein said insulator materialis a glass selected from the group of borosilicate glasses,potash-soda-barium glasses, pota'sh-soda-lead glasses, soda-lime glassesor alumina-silicate glasses.

21. The article as claimed in claim 21, wherein said glass is aborosilicate glass.

22. The article as claimed in claim 17, wherein said insulator materialis a ceramic material selected from the group of alumina, steatite,fosterite and beryllia.

23. The article as claimed in claim 19, wherein said Group I metals arecopper, 'silver or gold, said Group VIII metals are nickel-palladium orplatinum and said film-forming metals are tantalum, aluminum, niobium,titanium or zirconium.

24. The article as claimed in claim 17, wherein said insulator member isborosilicate glass or alumina and said metal 7 member and said elongatedmetal strip are tantalum or a nickel-iron alloy or a silver-gold alloy.

25. The electrolytic capacitor of claim 11, wherein said anode is afilm-forming metal selected from tantalum, niobium, aluminum, titaniumor zirconium.

26. The electrolytic capacitor of claim 25, wherein said anode istantalum, or niobium or aluminum; said metal member sealing said openend of said insulator member and said apertured metal member and saidelongated member are tantalum, niobium, aluminum, silver gold,palladium, platinum, alloys thereof or clad materials thereof; and saidinsulator member is glass or ceramic material.

27. The electrolytic capacitor as claimed in claim 26,

wherein said insulator material is a glass selected from the group ofborosilicate glasses, potash-soda-barium glasses, potash-soda-leadglasses, soda-lime glasses or alurnina-silicate glasses.

28. The electrolytic capacitor as claimed in claim 27, wherein saidglass is a borosilicate glass.

' 29. The electrolytic capacitor as claimed in claim 26, wherein saidinsulator material is a ceramic material selected from the group ofalumina, steatite, fosterite and beryllia.

30. The electrolytic capacitor of claim 26, wherein said anode and saidmetal member sealing said open end of said insulator member and saidapertured metal member and said elongated metal member are tantalum andinsulative member is borosilicate glass or alumina.

31. The electrolytic capacitor of claim 30. wherein said borosilicateglass includes up to about 65 weight percent silica, up to about 7weight percent alumina, up to about 18 weight percent boric oxide, up toabout 10 weight percent lithium oxide, up to 2 weight percent soda, upto about 3 weight percent potash, the remainder essentially bariumoxide.

32. The electrolytic capacitor of claim 26, wherein said anode istantalum and said metal member sealing said open end of said insulativemember is an alloy of up to about weight percent silver, the remainderessentially gold.

33. The electrolytic capacitor of claim 11, further including terminallead means attached to said metal member closing said one end of saidinsulator member on a side opposite to said side to which said elongatedmetal member is attached.

ii 1 i

1. An article of manufacture comprising: an electrical component withina container therefore, said container having at least one openingtherein; said electrical component having an electrically conductivelead member in electrical contact with said component; a seal memberclosing said opening in said container; said seal comprising; aninsulative member of glass or ceramic material having an aperturetherein; said insulative member being integrally bonded to a first metalmember along a first band interface, said first metal member having anaperture therein; said insulative member also being integrally bonded toa second metal member along a second bond interface, said second bondinterface being substantially parallel to said first bond interface,said second member closing the aperture in said insulative member; saidlead member passing through the aperture in said first metal member andthrough the aperture in said insulative member and into mechanicalengagement with said second metal member; said insulative member beingelongated in a direction substantially parallel to said first and secondbond interfaces.
 2. The article as claimed in claim 1, wherein saidmetal member is selected from the group of low-carbon steels, Group Imetals or alloys or clad metals thereof, Group VIII metals or alloys orclad metals thereof, film-forming metals or alloys or clad metalsthereof, iron-nickel alloys or clad metals thereof or chromium-ironalloys or clad materials thereof.
 3. The article as claimed in claim 2,wherein said insulator member is a glass selected from the group ofborosilicate glasses, potash-soda-barium glasses, potash-soda-leadglasses, soda-lime glasses or alumina-silicate glasses.
 4. The articleas claimed in claim 3, wherein said glass is a borosilicate glass. 5.The article as claimed in claim 2, wherein said insulator member is aceramic material selected from the group of alumina, steatite, fosteriteand beryllia.
 6. The article as claimed in claim 2, wherein said Group Imetals are copper, silver or gold, said Group VIII metals are nickel,palladium or platinum and said film-forming metals are tantalum,aluminum, niobium, titanium or zirconium.
 7. The article as claimed inclaim 1, wherein said insulative member is borosilicate glass or aluminaand said metal member and said elongated metal strip of metal aretantalum or a nickel-iron alloy or a silver-gold alloy.
 8. The articleas claimed in claim 7, wherein said metal member and said elongatedstrip of metal are tantalum.
 9. The arTicle as claimed in claim 7,wherein said metal member and said elongated metal strip are anickel-iron alloy including up to about 30 weight percent nickel, up toabout 18 weight percent cobalt, traces of manganese and silicon andcarbon, the remainder essentially iron.
 10. The article as claimed inclaim 7, wherein said metal member and said elongated metal strip are asilver-gold alloy including up to about 90 percent silver, the remainderessentially gold.
 11. An article according to claim 1 wherein saidarticle is a capacitor and said component is at least in part acapacitor anode.
 12. A capacitor according to claim 11 which is anelectrolytic capacitor.
 13. An article according to claim 1 wherein saidseal member is a hermetic seal.
 14. The hermetic seal of claim 13,wherein said aperture of said insulator member is about 10 mils or moreand said insulator member having a length and a width of about 50 milsor more, said metal member closing said one end of said aperturedinsulative member having a length and a width of about 50 mils or more,and said aperture of said apertured metal member having a diameter ofabout 10 mils or more and having a length and width of about 50 mils ormore.
 15. The hermetic seal of claim 14, wherein said elongated strip ofmetal is spaced from the inner wall of said aperture of said insulativemember and from the inner wall of said apertured metal member.
 16. Thehermetic seal of claim 15, wherein said elongated metal strip is a metalwire having a diameter of about 5 mils or more.
 17. The hermetic seal ofclaim 16, wherein the thickness of said insulative member is about 5mils or more, the thickness of said metal member closing said one end ofsaid apertured insulative member is about 10 mils or more and thethickness of said apertured metal member is about 1 mil or more.
 18. Thehermetic seal of claim 17, wherein said thickness of said aperturedmetal member is about 10 mils or more.
 19. The article as claimed inclaim 17, wherein said metal member is selected from the group oflow-carbon steels, Group I metals or alloys or clad metals thereof,Group VIII metals or alloys or clad metals thereof, film-forming metalsor alloys or clad metals thereof, iron-nickel alloys or clad metalsthereof or chromium-iron alloys or clad materials thereof.
 20. Thearticle as claimed in claim 17, wherein said insulator material is aglass selected from the group of borosilicate glasses,potash-soda-barium glasses, potash-soda-lead glasses, soda-lime glassesor alumina-silicate glasses.
 21. The article as claimed in claim 21,wherein said glass is a borosilicate glass.
 22. The article as claimedin claim 17, wherein said insulator material is a ceramic materialselected from the group of alumina, steatite, fosterite and beryllia.23. The article as claimed in claim 19, wherein said Group I metals arecopper, silver or gold, said Group VIII metals are nickel-palladium orplatinum and said film-forming metals are tantalum, aluminum, niobium,titanium or zirconium.
 24. The article as claimed in claim 17, whereinsaid insulator member is borosilicate glass or alumina and said metalmember and said elongated metal strip are tantalum or a nickel-ironalloy or a silver-gold alloy.
 25. The electrolytic capacitor of claim11, wherein said anode is a film-forming metal selected from tantalum,niobium, aluminum, titanium or zirconium.
 26. The electrolytic capacitorof claim 25, wherein said anode is tantalum, or niobium or aluminum;said metal member sealing said open end of said insulator member andsaid apertured metal member and said elongated member are tantalum,niobium, aluminum, silver gold, palladium, platinum, alloys thereof orclad materials thereof; and said insulator member is glass or ceramicmaterial.
 27. The electrolytic capacitor as claimed in claim 26, whereinsaid insulator material is a glass selecteD from the group ofborosilicate glasses, potash-soda-barium glasses, potash-soda-leadglasses, soda-lime glasses or alumina-silicate glasses.
 28. Theelectrolytic capacitor as claimed in claim 27, wherein said glass is aborosilicate glass.
 29. The electrolytic capacitor as claimed in claim26, wherein said insulator material is a ceramic material selected fromthe group of alumina, steatite, fosterite and beryllia.
 30. Theelectrolytic capacitor of claim 26, wherein said anode and said metalmember sealing said open end of said insulator member and said aperturedmetal member and said elongated metal member are tantalum and insulativemember is borosilicate glass or alumina.
 31. The electrolytic capacitorof claim 30, wherein said borosilicate glass includes up to about 65weight percent silica, up to about 7 weight percent alumina, up to about18 weight percent boric oxide, up to about 10 weight percent lithiumoxide, up to 2 weight percent soda, up to about 3 weight percent potash,the remainder essentially barium oxide.
 32. The electrolytic capacitorof claim 26, wherein said anode is tantalum and said metal membersealing said open end of said insulative member is an alloy of up toabout 90 weight percent silver, the remainder essentially gold.
 33. Theelectrolytic capacitor of claim 11, further including terminal leadmeans attached to said metal member closing said one end of saidinsulator member on a side opposite to said side to which said elongatedmetal member is attached.